I think this note was added to bt(4) after 2.3:
The PCI versions of this card will require the Buslogic BIOS "Advanced
Options" suboption called "Set ISA Compatible IO Port" to be set to the
value "Primary" or "Alternate". Some cards have an option called "Set
host adapter IO port address as default" instead; for those boards you
should set the value to "false".
- todd